Spinal nerve decompression procedures may require stabilization of the operative treatment level(s), which is generally accomplished by fusion. In cases where a high degree of stabilization is not required, a posterolateral fusion is performed. This will generally include placing autogenous bone graft on posterolateral aspects of the spine (transverse processes, facet joints, lamina) and may include permanent transpedicular instrumentation, such as metallic facet and translaminar facet screws or pedicle screw/rod or plate systems. Significant morbidity can be attributed to the destabilizing surgical procedure required to achieve the fusion. Further, the presence of permanent metallic hardware can cause problems such as metallosis, fracture and interference with MRI and CT evaluation.
US Published Patent Application US 20020068975 (“Shaolian”) discloses formed in place orthopedic fixation devices comprising inflatable members inflated with hardenable media. Shaolian et al. does not disclose hardenable media that is resorbable, osteoconductive, or osteoinductive. See also US 20020082598, US 20020082600, US 20020198526, US 20040006341, US 20040006344 and WO2003020110.
U.S. Pat. No. 5,571,189 (“Kuslich”) discloses a flexible fabric bag packed with a biological fill composition that allows bone ingrowth through the bag. Kuslich further discloses a sausage-shaped container prefilled with fill composition and positioned against the bone of adjacent vertebrae. The containers become very rigid over time and attach via bone ingrowth to the vertebrae, ultimately to provide a fusion.
In particular, in FIGS. 11 and 12 of Kuslich, a bag is depicted as a sausage-shaped container 146 which is not implanted into a disc cavity. Rather, one or more of the bag containers 146, prefilled with fill composition 52, are positioned against the bone of adjacent vertebrae. The bone may be toughened to a bleeding surface to hasten bone growth into the containers 146. According to Kuslich, as time goes by, the containers will become very rigid and will be attached via bone ingrowth to both vertebrae where they contact native bone to provide a safe, simple fusion. The bags provide containment of the bone-growth composition to ensure that the fusion takes place where indicated.
Kuslich does not disclose a filled bag that is fixed to the adjacent vertebrae at the time of implantation. Accordingly, this device is subject is undesired movement prior to fusion.
PCT Patent Publication WO00245765 (“Sybert”) disclosed an osteogenic band affixed to two or more vertebrae on the posterior side of the spine. Sybert does not disclose an in-situ hardenable composition.
U.S. Pat. No. 6,723,095 (Hammerslag) discloses methods of spinal fixation involving the application of a liquid medium which cures, hardens, polymerizes or otherwise serves to bind adjacent vertebrae together. Hammerslag discloses a preferred embodiment in which the liquid medium is a low viscosity cyanoacrylate-based adhesive, a composition that does not promote fusion.
Although Hammerslag further teaches that “use of a medium to fix the articulate processes may be combined with methods which involve stimulating the growth of a bony mass or fusion body to fix the spine.”(7, 24-27), Hammerslag does not disclose fusion of the postero-lateral aspects of adjacent vertebrae.